One known fuel injector, designed as a so-called multi-orifice fuel injector for internal combustion engines, see German Published Patent Appln. No. 10 2005 036 951, has a valve seat member accommodated at its end in a hollow cylindrical valve seat support, which, using an inner body wall, bounds a valve chamber that is in connection to a fuel supply. A valve seat is developed on the inner body wall of the valve seat support. A plurality of spray orifices are situated in the valve seat body, which, in the inner body wall, namely in the range of the body wall enclosed by the valve seat, has orifice entry openings situated, and in the outer convex body wall of the valve seat body, facing away from the valve chamber, has orifice exit openings. Each of the plurality of spray orifices has an orifice entry section having a small cross section, bordered upstream by the orifice entry opening and an orifice exit section having a larger cross section that is bordered downstream by the orifice exit opening. Together with a closing member, the valve seat forms a sealing seat lying upstream of the spray orifices that is axially displaceable in the valve seat support and is drivable for the lift motion. Within the range of the body wall of the valve seat body enclosed by the orifice entry openings of the spray orifices, a blind-end bore having a blind-end bore opening towards the valve chamber has been worked into the body wall. Such a blind-end bore is used as a stabilizing volume for damping a highly turbulent fuel flow which, at full lift of the valve member in this area, develops by an excess of fuel for the spray orifices.
It has turned out that, in the closing phase of the valve at the end of the injection, as a result of the inertia injection orifice flow, an underpressure is created in the blind-end bore and thereby a partial return flow of the fuel to the blind-end bore takes place, Because of this return flow, a clear reduction in the preparation quality of the fuel is created, which increases the soot emission in the exhaust gas and promotes coking, i.e. deposits from combusted fuel, at the orifice exit openings of spray orifices.